Preparation and characterization of highly active nanosized strontium-doped lanthanum cobaltate catalysts with high surface areas

Abstract

La1−xSrxCoO3-δ (x=0, 0.4) nanoparticles have been prepared using the citric acid complexing-hydrothermal synthesis coupled method and citric acid complexing method. The physico-chemical properties of these materials were characterized by means of X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM), element analysis (EDX), X-ray photoelectron spectroscopic (XPS), oxygen temperature-programmed desorption (O2-TPD), hydrogen temperature-programmed reduction (H2-TPR) as well as surface area measurements and oxidation state titration. Their catalytic performance was examined for the total oxidation of ethylacetate (EA). It is found that the La1−xSrxCoO3−δ (x=0, 0.4) catalysts were single-phase and rhombo-hedrally-structured perovskites and their surface areas ranged from 16 to 26 m2/g. The Sr-doped sample derived from the coupled procedure was uniformly distributed nanoparticles with a short rod-shaped morphology. The doping of Sr (i) enhanced the concentrations of Co3+ and oxygen vacancies, (ii) increased the amount of oxygen adsorbed on the surface at low temperatures, (iii) promoted the mobility of lattice oxygen, and (iv) improved the properties of redox. The La0.6Sr0.4CoO2.78 catalyst prepared by the citric acid complexing-hydrothermal synthesis coupled strategy performed the best in the oxidation of EA, furthermore no partially oxidized products were formed. Based on the above results, we conclude that in addition to the surface area, the catalytic activity of the perovskite-type oxide nanoparticles was associated with the structural defect (oxygen vacancy) concentration and redox ability.